Conjugated linoleic acid (CLA) is the general term used to refer to a class of positional isomers of the omega-6 essential fatty acid octadecadienoic acid or linoleic acid. CLA contains conjugated double bonds (i.e. double carbon bonds separated by a single carbon bond). CLA is found naturally in the meat and dairy foods derived from ruminant animals where it is produced by the anaerobic bacteria, Butyrivibrio fibrisolvens, which is present in the rumen of these animals. However, CLA comprises a relatively minor proportion of the total fatty acid content contained in meats or dairy products (e.g. only about 0.5% per gram of fat). Although CLA occurs naturally in relatively small amounts, it is commonly produced industrially through the partial hydrogenation of linoleic acid purified from sources such as safflower or sunflower. As discussed in U.S. Pat. No. 6,015,833 entitled “Conjugated Linoleic Acid Compositions,” the use of sunflower and safflower oil is preferred because of their high native 9, 12 linoleic acid content, and also because they have low levels of contaminating residues that can result in a less pure product.
Since the discovery of CLAs by researchers at the University of Wisconsin in 1978, most attention has been directed towards two particular CLA isomers, the cis-9, trans-11 (c9,t11) CLA and trans-10, cis-12 (t10,c12) CLA isomers. The interest in these two isomeric species of CLA is related to the beneficial biological effects associated with their consumption. Some of the biologically advantageous activities that have been attributed to the consumption of c9, t11 CLA and t10, c12 CLA isomers include anticarcinogenic activity, antiatherogenic activity, and antidiabetic activity. In addition, it has been reported that consumption of CLA can decrease an individual's body fat to body mass ratio, and several studies have reported that CLA has beneficial effects on certain aspects of immune system function.
Interestingly, several studies of the physiological effects of CLA suggest that the health benefits are mediated differentially by specific CLA isomers. For example, studies have shown that c9, t11 CLA can enhance growth in rodents, but only t10, c12 CLA was shown to decrease blood lipoproteins, and triacylglyerides in hamsters and affect lean body mass in mice. Furthermore, in vitro experiments using preadipocytes indicate that only the t10, c12 CLA isomer was able to inhibit lipoprotein lipase activity, inhibit stearyl CoA desaturase activity, increase peroxisome proliferator activated receptor expression, and increase lipid oxidation.
For adult humans the daily required amount of CLA has been reported in various studies to be between about 80 milligrams to as much as about 50 grams per day. Because the typical diet does not provide this amount of CLA, dietary supplements are used to increase CLA intake to the desired or recommended level. Although various delivery means have been used, the most widely used and commonly marketed forms of CLA supplements are either liquid compositions, or ingestible capsules or tablets composed of gelatin or cellulose that contain 500-750 milligrams of CLA per tablet. However, these forms of CLA have several important limitations which make them undesirable. For example, because of the relatively large daily doses of CLA that may be required (e.g. about 3 grams or more per day for adults), individuals are faced with the undesirable choice of consuming a large volume of a liquid containing CLA, having to swallow relatively large capsules or tablets, having to swallow many capsules or tablets per day, or a combination thereof. Additionally, in many cases the transport of a large volume of liquid or a large number of capsules necessitates that the individual carries a bulky, inconvenient and/or cumbersome container, and have a ready supply of water or other liquid to assist in consuming the supplement.
Furthermore, the prior forms of CLA supplements are generally exposed to air during storage or use, particularly when provided in containers having multiple doses of the supplement. Exposure to air results in oxidation of the CLA fatty acids, which alters their structure, reduces or eliminates their beneficial properties, and reduces their shelf-life. To ameliorate the effects of oxidation, CLA is typically packaged with one or more chemical antioxidants, for example, lecithin, tocopherols, ascorbate, or ascorbyl palmitate. However, the inclusion of antioxidants results in added costs to the manufacturer, and because of the progressive oxygen exposure, only offers a limited extension of the overall shelf-life.
It is an object of the present invention to overcome one or more of the above-described drawbacks or disadvantages of the prior art. Accordingly, the present invention provides a nutritional composition comprising CLA in an emulsion. The composition may also contain one or more substances to enhance the flavor or texture of the composition, or to provide additional nutrients. The nutritional composition may be manufactured in a manner to minimize the effects or exposure of the CLA to oxygen, and the composition may be hermetically sealed in a container, such as for example a foil pouch, for transportation and storage. Additionally, the container may be sized to contain a single daily dose of CLA.